1. Field of the Invention
The present invention relates to a vibration generating device used in various types of electronic units and to an input device that uses the vibration generating device.
2. Description of the Related Art
In the electronic unit field, input devices such as touch panels and touch pads have been frequently used in recent years. This input device is such that when a manipulator (user) brings a fingertip into contact with the manipulation surface, the input device detects the coordinate position of the fingertip on the manipulation surface according to a change in a capacitance value or the like and enables an input manipulation matching the coordinate position. For example, this type of input device is installed on the front surface of a display device such as a liquid crystal display (LCD). When the user places a fingertip on a desired manipulation area displayed on the screen of the display device, manipulation contents of the manipulation area are executed.
With this type of input device, when the user manipulates the input device by bringing the user's fingertip into contact with the manipulation surface, a difference in sense transmitted to the fingertip does not occur between before and after the manipulation (input), so the user has not been able to obtain a manipulation sense (manipulation feeling). In view of this, a feeling stimulus generating device that gives a feeling stimulus (feeling feedback) to the user's fingertip has been conventionally proposed, and there has been a case in which an input device is used in combination with this feeling stimulus generating device. As a typical example of this feeling stimulus generating device, a type of stimulus generating device that gives vibration to impart a feeling stimulus is most used.
As this vibration type of feeling stimulus generating device, International Publication No. WO2012/067178 proposes an electromagnetic actuator 900 as illustrated in FIGS. 10A, 10B, 11A and 11B. FIGS. 10A and 10B illustrate the electromagnetic actuator 900 in a conventional example. FIG. 10A is a schematic longitudinal cross-sectional view, and FIG. 10B is a structural diagram on which the main constituent components (actuator portion) of a portion XB indicated in FIG. 10A are extracted. FIGS. 11A and 11B illustrate magnetic path analysis results indicating the effect of the actuator portion indicated in FIG. 10B; FIG. 11A is a magnetic flux line diagram in an initial state, and FIG. 11B is a magnetic flux line diagram in a state in which a current is supplied to a coil 918.
The electromagnetic actuator 900 indicated in FIGS. 10A and 10B has: a first fixed iron core 912 and a second fixed iron core 914, which are disposed opposite to each other with a predetermined gap interposed in the direction of an axial line O; a movable iron core 916 disposed so as to be movable along the axial line O in the vicinity of this gap; and a coil 918 that exerts magnetic fields around the two fixed iron cores (first fixed iron core 912 and second fixed iron core 914) and the movable iron core 916 to form magnetic paths in them and move the movable iron core 916 along the axial line O. Basically, these members are formed in a rotationally symmetrical form, that is, in a circular form, and are accommodated in a cylindrical housing 920.
With the electromagnetic actuator 900, when a current is supplied to the coil 918 in an initial state indicated in FIG. 11A, a magnetic attractive force is generated for the movable iron core 916 from each of the two fixed iron cores (first fixed iron core 912 and second fixed iron core 914). At this time, the second fixed iron core 914 and a magnetic flux inducing part 934, extending in the direction of the axial line O, of the movable iron core 916 mainly undertake an effect of inducing a magnetic flux, and the first fixed iron core 912 and a magnetic flux action part 932, extending in a direction crossing the axial line O, of the movable iron core 916 mainly undertake an attraction effect. Due to this, the magnetic attractive force on the same side as the first fixed iron core 912 is larger than the magnetic attractive force on the same side as the second fixed iron core 914. Therefore, when a current is supplied, the movable iron core 916 moves toward the first fixed iron core 912 and enters a state indicated in FIG. 11B. Due to the movement of the movable iron core 916 at this time, vibration is generated.